The third milestone in making Malleatus production ready was to allow user control of the deformation of the boundary surfaces. I developed an interface such that the user can code how the boundaries move and pass/receive information to Malleatus. The exchange of information is shown below:

For this post, I revisited the F-16. I will show animations of twisting and bending of the the wing using the user-coded boundary movement library. Additionally, this case was run using small scale parallelization (up to 8 processors).Continue reading→

The next milestone reached in the continued development of Malleatus was the determination of user input. As always, we want to provide enough control to the user while not overwhelming them with unnecessary knobs. I was able to minimize the user input to three values. The first two control the amount of influence the movement of boundaries have on grid points; the values must lie between 0.0 and 1.0. The final input controls the unfolding of folded faces algorithm. Additionally, initial parallelization work has begun.

For this post, I revisited the Onera M6 wing. I wanted to show solutions obtaining under bending and twisting using the new user input. The conditions used for the simulation were: M= 0.8395, angle of attack = 3.06 degrees, Pressure = 98,920.475 Pa and T was 300 degrees K.Continue reading→

Last year the focus of Bob’s Research Corner was to report on the evaluation and testing of various grid deformation techniques. This year, I’m going to chronicle the transformation of last year’s research code into a production utility. I’ve decided to name this utility Malleatus. Malleatus means “beaten or shaped by a hammer” which invokes images of using a hammer to bend and shape a grid. But grid deformation also requires a delicate hand, and the name references malleus which is the hammer-shaped bone in the middle ear that transmits vibrations of the eardrum.Continue reading→

In this article, I will focus on the improved twisting utilizing the unfolding folded faces (UFF) algorithm discussed in the last BRC post. The new twisting limits for both the Onera M6 wing and the F-18C vertical tail will be shown. See “Bob’s Research Corner: Grid Def – Twist” for the previous twist limits.Continue reading→

For the last several months, I’ve been working on an algorithm to increase the amount of bending my grid deformer can handle before the grid becomes invalid. I’m finally to the point where I believe I have a reliable algorithm that unfolds folded faces resulting from grid deformation. For this article, I will focus on bending only. I will show the increased bending limit for both the Onera M6 wing and the F-18C vertical tail shown previously in “Bob’s Research Corner: Grid Def – Bending”.Continue reading→

In this post, I’ll present the twisting results of my grid deformation code. I’ve taken the same grids (Onera M6 wing and the F-18C vertical tail) and applied a twist along the mid-chord. For information about the grids and the bending results, you can read “Bob’s Research Corner: Grid Def – Bending”. Twisting along the mid-chord is based on the square of the span location times a maximum twist angle.

On the Onera M6 wing, the maximum twist angle achieved before encountering folded faces was 10.5 degrees. The maximum twist occurs at the wing tip. This is an ok twist amount just like the bending result. The results are shown below, first with a video of the wing twisting over 25 time-steps followed by still images comparing the original versus deformed grid. The original grid is shown in red while the deformed grid is shown in blue.Continue reading→

For the last month or so, I’ve been focusing on 3-D grids with deforming boundaries. I split this into two main categories: bending and twisting. This article will focus on bending only. I will make a post about twisting in the near future.

The goal of this project is to develop a grid deformation algorithm capable of handling larger than real world deformations. And by handling, I mean producing valid Cobalt grids. If I’m successful, then our customers can simulate real world cases such as aeroelastic deformations.

The first test case I’m going to show is an Onera M6 wing grid. The grid contains 2,276,261 cells (1,832,756 tets, 17,642 pyramids and 425,863 prisms) and is valid for Navier-Stokes simulations. The bending function used is a quadratic displacement based on an amplitude multiplying the square of the span location. The maximum deflection of the tip I could get was 9.25% of the span; anything larger resulted in the dreaded folded faces. For those not familiar with a folded face, first, define a face as the interface between two cells. When flow leaves one cell across a face, it enters the other cell. When a face becomes folded, then the centroids of both cells lie on the same side of the face. This means flow leaving one cell through the face, also leaves the other cells. This is VERY bad as conservation cannot be conserved! That being said, a 9.25% of the span deflection is not bad. This might be good enough for real world cases. Of course, I’d like to do better. The video below shows the bending of the wing compared to the original. And the images show the original grid versus the deformed grid.Continue reading→

Welcome to Bob’s Research Corner! In the past, we did not have a convenient way to provide research news to you – unless you considered spamming your email occasionally a good way :). When I redesigned the website, I made it very easy to post quick news updates. You can thank Bill for the idea (or maybe blame him — your choice!) I plan to provide updates on my research once or twice a quarter. It’s up to you if you want to read my ramblings…..

With the release of v7.0, I’ve been able to shift my focus from Overset to a new project. I had several ideas/interests and decided to look into Grid Deformation. Cobalt has been able to calculate solutions on deforming grids since the release of v6.0 (February 2013). Our plan was always to interface with a 3rd party grid deformer. Unfortunately, that has not happened yet. So I decided it was time to see if I could develop our own grid deformation tool…

I’ve spent the last month looking at grid deformation methods, writing little research codes to test out ideas, etc. I’m finally ready to provide a little preview. It’s only 2-D with rigid boundaries — but the interior of the grid must deform. Every step has a valid Cobaltgrid…I’m ok with +/-90 degree rotation! If you have any questions, leave a comment or send me an email. Check back in a few weeks when I hope to have more to show you.

Solutions

The equilibrium air module uses the curve fits of Tannehill, et al. to calculate the thermodynamic and molecular properties of air when intermolecular forces become important. As temperature becomes large, dissociation and eventually ionization occurs. The thermodynamic properties of air become dependent on two variables (T = T(P,e)). For hypersonic flows, this has the effect of weakening the strength of a shock wave. The table below shows the temperatures at which dissociation and ionization become important. Molecular vibrations start occurring around T=600 K which is the temperature value where starts γ changing.